Boris Johnson loves U-turns. Let's hope this extends to a no-deal Brexit

Britain could be the first developed economy to be sabotaged by maths. Not by war, ideology or disease, but maths. The prime minister is said to be mesmerised by models.

Related: Failure of Brexit talks could lead to terrorism intelligence delays, say Lords

One is the coronavirus model of a “second spike” and half a million deaths, creation of Imperial College London statisticians, led by the epidemiologist Neil Ferguson. The other is the Brexit model of Professor Patrick Minford, forecasting a surge of 4% in British growth in the event of a hard Brexit. Both modellers have their critics. But no matter. To Boris Johnson, the model is god. Forget common sense. Maths cannot lie. The models hover over today’s Downing Street like two swords of Damocles.

Johnson can reasonably argue that he was not alone in following Imperial College to blanket lockdown. He meant well. But now he is trapped by it. Despite his project fear and its poll approval, lockdown failed to stem Europe’s second worst death rate. According to the OECD, it is also about to inflict on Britain Europe’s worst recession – an 11.5% fall in GDP, compared with Germany’s 6.6%. Unemployment without equal since the 1930s may result.

One might think that, having cut off the economy’s two legs, Johnson might be kind to its arms. But no. This week he and his Brexiter colleague Michael Gove indicated that talks with the EU on a trade deal had stalled. There was no way they would seek the extension on offer at the end of this month. They are putting it about that, with the economy in ruins anyway, no one will actually notice more blood spilt over stalled EU trade.

Like many half-hearted remainers, I have accepted Brexit as a new reality. But I could never imagine no trade deal with the EU. It was and is barking mad. As with blanket lockdown, no-deal Brexit is treated by Johnson and Gove as undergraduate psychology – of bluff, double-bluff and debating points. They regard the EU’s Michel Barnier as the cad of the lower fifth. Put him against the wall, they jeer, and he will fold.

There is absolutely no reason for failing to extend the current EU talks, at least until heads on both sides can clear. The British economy, partly through the government’s own fault, faces appalling contraction. The economy’s second biggest sector, hospitality and tourism, has been devastated.

Johnson may think Britons are so bound up in the horrors of his first model that they will not notice the horrors of the second. Apart from such irresponsibility, that cannot apply to businesses and their employees. British exporters face an instant tariff wall from January. Farmers may have to slaughter animals. Aviation, policing, and food and medicine supply chains will choke. Banking arrangements may be cobbled together, but the trickle of financial emigration to Europe’s capitals will become a flood. And for what? So Johnson can keep his appointment with his own chosen date.

Searchers after comfort may find some in the prime minister’s addiction to U-turns. He made a significant one last year when he agreed to an unavoidable customs border with Northern Ireland. Peering through the murk, we can see the hope of a compromise on fish, where at least Britain has right on its side.

Other EU concessions are harder to discern. A grownup arrangement should be possible on trade arbitration. One is less plausible on common trading standards. Compliance to such standards is the essence of a sophisticated free market between adjacent economies, but Johnson seems averse. The idea that a deal with the US might ever compensate for the EU, let alone now, is fantastical.

In other words, a version of the old single-market option of sharing Europe’s “economic area” should make as much sense to a Eurosceptic as to a former remainer. It is said that the necessary concessions – or U-turns – could be cobbled together by Christmas. But this involves Downing Street genuinely wanting it.

Why Johnson should want to put British businesses and their workers through the hell of yet more uncertainty is a mystery. He says he must keep faith with those who voted for Brexit, but this is infantile. They were a narrow majority, and were never asked to vote for no deal. A poll last month was emphatic. Three-quarters of respondents do not want to leave the EU without a deal. That includes 64% of Tories and 57% of leavers.

There cannot be a majority for no deal in parliament. Keir Starmer and the opposition have a duty to do all they can to force Downing Street to reverse its intransigence. They must stop Johnson doubling-down on insanity, and declare death to the models and the maths.

• Simon Jenkins is a Guardian columnist